Traditionally, vehicles have been provided with antennas mounted in different locations of the vehicle. Usually, these antennas were located at the rear window and/or on the roof.
Over the years, the number of radio-communication services has increased and, in consequence, the number of antennas required for providing these services.
Also, aesthetic and aerodynamic trends have changed and, over the years, satisfying customer tastes has become essential in the automotive industry. Lately, customer tastes generally lead to vehicles having a streamlined and smooth appearance, which interfere with providing the vehicle with multiple and dispersed antennas.
Thus, both for meeting customer tastes and providing all the radio-communication services possibly demanded by the driver, the automotive industry is tending to integrate in a single module all the communication modules specifically designed for providing one communication service, such as telephony, AM/FM radio, satellite digital audio radio services (SDARS), global navigation satellite system (GNSS), or digital audio broadcasting (DAB).
The integration of multiple antenna units in a single global antenna module leads to achieve great advantages in costs, quality and engineering development time.
This global antenna module is also conditioned by meeting customer tastes. For that, it would be desirable to reduce the size of the antenna module in order to maintain the streamlined appearance of the vehicle. In particular, it would be desirable to reduce the length of the antenna module to facilitate the integration of other antennas configured for providing other communication services without having to increase the length of the antenna module.
However, a reduction in the length of the antenna module affects its performance, specially, the level of isolation between the two LTE antennas. This reduction in isolation directly affects the LTE communication.
Then, it would be desirable to develop an improved MIMO antenna system for a vehicle that is capable of providing communication at all 4G frequency bands of operation while having a length reduction.